ALLAH (SWT) Says:

"This day I have perfected your religion for you, completed My favour upon you, and have chosen for you Islam as your religion." (Surah Al Ma'idah 5:3)

ALLAH (SWT) Says:

"Will they not, then, try to understand this Quran? Had it come from anyone other than Allah, they would have found in it many an inner contradiction." (Surah Al-Nisa' 4:82)

Quote

From speech of Jafar to the King of Abyssinia about Muhammad (peace be upon him)

"He called us to worship God alone... he commanded us to speak the truth, to honor our promises, to be kind to our relations, to be helpful to our neighbors, to cease all forbidden acts, to abstain from bloodshed, to avoid obscenities and false witness..."